U.S. patent application number 16/073666 was filed with the patent office on 2019-01-31 for cooling system for nuclear reactor.
The applicant listed for this patent is Terrestrial Energy Inc.. Invention is credited to David LEBLANC, Anthonius C. RODENBURG.
Application Number | 20190035510 16/073666 |
Document ID | / |
Family ID | 59396800 |
Filed Date | 2019-01-31 |
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United States Patent
Application |
20190035510 |
Kind Code |
A1 |
LEBLANC; David ; et
al. |
January 31, 2019 |
COOLING SYSTEM FOR NUCLEAR REACTOR
Abstract
A cooling system to remove decay heat removal from a nuclear
core of a nuclear reactor when the nuclear reactor cesses to
operate due to unforeseen conditions such as, for example, loss of
electrical power to pumps circulating the primary coolant in the
nuclear reactor. The cooling has a conduit structure that defines a
sealed closed circuit through which a cooling fluid circulates
through natural convection. In some embodiments, the cooling system
of the present disclosure is always functioning. That is, the
cooling system continuously extracts heat from the nuclear core. In
these embodiments, the cooling system does not need to be actuated
in any way when the nuclear reactor shuts down unexpectedly. In
other embodiments, the cooling system can be turned on
automatically upon loss of electrical power.
Inventors: |
LEBLANC; David; (Ottawa,
CA) ; RODENBURG; Anthonius C.; (Mississauga,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Terrestrial Energy Inc. |
Oakville |
|
CA |
|
|
Family ID: |
59396800 |
Appl. No.: |
16/073666 |
Filed: |
January 27, 2017 |
PCT Filed: |
January 27, 2017 |
PCT NO: |
PCT/CA2017/050095 |
371 Date: |
July 27, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62288790 |
Jan 29, 2016 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G21C 15/253 20130101;
G21C 15/26 20130101; Y02E 30/30 20130101; Y02E 30/40 20130101; G21C
19/08 20130101; G21C 15/18 20130101 |
International
Class: |
G21C 15/18 20060101
G21C015/18; G21C 15/253 20060101 G21C015/253; G21C 15/26 20060101
G21C015/26; G21C 19/08 20060101 G21C019/08 |
Claims
1. A cooling system for a nuclear reactor, the system comprising: a
conduit structure defining a sealed closed circuit, the conduit
structure being formed outside the nuclear reactor, the conduit
structure to hold a gas therein, the conduit structure having a
first portion in thermal contact with the nuclear reactor, the
first portion configured to transfer heat from the nuclear reactor
to the gas present in the first portion, the heat transferred to
the gas to heat the gas in order to obtain heated gas, the conduit
structure having a second portion located higher than the first
portion, the second portion being in thermal contact with an
environment, the conduit structure configured for the heated gas to
propagate, by natural convection, from the first portion to the
second portion, the heated gas to propagate through the second
portion and to transfer heat to the environment as the heated gas
propagates through the second portion, the heated gas to cool
during propagation through the second portion in order to obtain
cooled gas, the conduit structure defining a return portion for
returning the cooled gas to the first portion, the cooling system
configured to continuously remove heat from the nuclear reactor
during operation of the nuclear reactor and when the nuclear
reactor stops operating and generates decay heat.
2. The system of claim 1 wherein the first portion of the conduit
structure is configured to receive heat from the nuclear reactor
through at least one of heat radiation, heat conduction, and heat
convection.
3. The system of claim 1 or claim 2 wherein the first portion is
cylindrically shaped and surrounds the nuclear reactor.
4. The system of any one of claims 1-3 wherein the second portion
of the conduit structure defines a wall.
5. The system of claim 4 wherein the second portion of the conduit
structure further defines a ceiling portion formed above the wall
portion.
6. The system of claim 4 wherein the second portion of the conduit
structure further defines a roof portion that extends over the
ceiling portion.
7. The system of claim 5 or claim 6 wherein the ceiling portion
extends from the wall portion at an angle ranging between 2 and 10
degrees.
8. The system of claim 6 or claim 7 wherein the roof portion
defines a dome.
9. The system of claim 4 wherein the second portion of the conduit
structure further defines first upper portion formed above the wall
portion.
10. The system of claim 4 wherein the second portion of the conduit
structure further defines a second upper portion that extends over
the first upper portion.
11. The system of claim 9 or claim 10 wherein the first upper
portion extends from the wall portion at an angle ranging between 2
and 10 degrees.
12. The system of claim 10 or claim 11 wherein the second upper
portion defines a dome.
13. The system of any one of claims 1-3 wherein the second portion
comprises a cooling tower.
14. The system of any one of claims 1-13 wherein the conduit
structure further comprises a vault far storing spent nuclear fuel,
a riser for fluidly connecting the vault to the second portion, and
an ancillary conduit fluidly connecting the vault to the return
portion.
15. The system of any one of claims 1-14 wherein the gas includes
at least one of air, nitrogen and carbon dioxide.
16. The system of anyone of claims 1-15 further comprising: one or
more than one vault for storing spent nuclear fuel; and a vault
cooling system for cooling the one or more than one vault, the
vault cooling system comprising: an additional conduit structure
defining an additional sealed closed circuit, the additional
structure to hold another gas therein, the additional conduit
structure having a first portion in thermal contact with the one or
more than vault, the first portion of the additional conduit
structure configured to transfer heat from the one or more than one
vault to the other gas present in the first portion of the
additional conduit structure, the heat transferred to the other gas
to heat the other gas in order to obtain another heated gas, the
additional conduit structure having a second portion located higher
than the first portion, the second portion of the additional
conduit structure being in thermal contact with another
environment, the additional conduit structure configured for the
heated other gas to propagate, by natural convection, from the
first portion of the additional conduit structure to the second
portion of the additional conduit structure, the heated other gas
to propagate through the second portion of the additional conduit
structure and to transfer heat to the other environment as the
heated other gas propagates through the second portion of the
additional conduit structure, the heated other gas to cool during
propagation through the second portion of the additional conduit
structure in order to obtain cooled other gas, the additional
conduit structure defining a return portion for returning the
cooled other gas to the first portion of the additional conduit
structure, the vault cooling system configured to remove heat from
the one or more than one vault during operation of the nuclear
reactor and when the nuclear reactor stops operating.
17. The system of claim 16 wherein the environment and the other
environment are the same.
18. The system of claim 1 or claim 17 wherein the environment is an
outside environment.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to cooling systems for
nuclear reactors. In particular, the present disclosure relates to
a cooling system for removing decay heat from a reactor.
BACKGROUND
[0002] Previous systems for the fail-safe removal of decay heat of
a nuclear reactor have been proposed involving the natural
circulation of outside air past the reactor vessel or a guard
vessel surrounding the reactor. Decay heat being the residual heat
given off by fission products after a nuclear reactor is shut down.
Such air cooling systems are possible for reactors that can
effectively move decay heat to the walls of the reactor, typically
by an internally contained liquid such as liquid sodium or lead
coolant in some fast reactor designs. When the power density within
the reactor vessel is not too high, the decay heat of such a system
can be effectively be removed by those systems.
[0003] One drawback is the relatively close proximity of a
potential release pathway to the environment in a severe accident
scenario. Another drawback is the potential activation of the
passing outside air by neutrons emitted from the reactor and the
creation of activated Argon 41. Whereas in sodium or lead cooled
fast reactor concepts there is ease to provide a thick, neutron
absorbing layer of sodium or lead between the reactor core and the
reactor vessel, in other potential use such as with Molten Salt
Reactors (MSR) or Fluoride cooled High temperature Reactors (FHR),
where decay heat can also be transmitted effectively to the reactor
vessel wall, such internal neutron shielding is more problematic
and avoiding activation of outside air is problematic.
[0004] Therefore, improvements in decay heat removal systems are
desirable.
SUMMARY
[0005] In a first aspect, the present disclosure provides a cooling
system for a nuclear reactor. The system comprises: a conduit
structure defining a sealed closed circuit. The conduit structure
is formed outside the nuclear reactor. The conduit structure is to
hold a gas therein. The conduit structure has a first portion in
thermal contact with the nuclear reactor. The first portion is
configured to transfer heat from the nuclear reactor to the gas
present in the first portion. The heat transferred to the gas is to
heat the gas in order to obtain heated gas. The conduit structure
has a second portion located higher than the first portion. The
second portion is in thermal contact with an environment. The
conduit structure is configured for the heated gas to propagate, by
natural convection, from the first portion to the second portion.
The heated gas is to propagate through the second portion and to
transfer heat to the environment as the heated gas propagates
through the second portion. The heated gas is to cool during
propagation through the second portion in order to obtain cooled
gas. The conduit structure defines a return portion for returning
the cooled gas to the first portion. The cooling system is
configured to continuously remove heat from the nuclear reactor
during operation of the nuclear reactor and when the nuclear
reactor stops operating and generates decay heat.
[0006] In some instances, the first portion of the conduit
structure can be configured to receive heat from the nuclear
reactor through at least one of heat radiation, heat conduction,
and heat convection.
[0007] In some instances, the first portion can be cylindrically
shaped and surround the nuclear reactor.
[0008] In some instances, the second portion of the conduit
structure can define a wall.
[0009] In some instances, the second portion of the conduit
structure can further define a ceiling portion formed above the
wall portion.
[0010] In some instances, the second portion of the conduit
structure can further define a roof portion that extends over the
ceiling portion.
[0011] In some instances, the ceiling portion can extend from the
wall portion at an angle ranging between 2 and 10 degrees.
[0012] In some instances, the roof portion defines a dome.
[0013] In some instances, the second portion can comprise a cooling
tower. The cooling tower can define a hyperbolic shape.
[0014] In some instance, the conduit structure further comprises a
vault for storing spent nuclear fuel, a riser for fluidly
connecting the vault to the second portion, and an ancillary
conduit fluidly connecting the vault to the return portion.
[0015] In some instances, the gas can include at least one of air,
nitrogen and carbon dioxide.
[0016] In some instances, the system can further comprise one or
more than one vault for storing spent nuclear fuel; and a vault
cooling system for cooling the one or more than one vault. The
vault cooling system comprises: an additional conduit structure
defining an additional sealed closed circuit The additional
conduits structure is to hold another gas therein. The additional
conduit structure has a first portion in thermal contact with the
one or more than vault. The first portion of the additional conduit
structure is configured to transfer heat from the one or more than
one vault to the other gas present in the first portion of the
additional conduit structure. The heat transferred to the other gas
is to heat the other gas in order to obtain another heated gas. The
additional conduit structure has a second portion located higher
than the first portion and the second portion of the additional
conduit structure is in thermal contact with another environment.
The additional conduit structure is configured for the heated other
gas to propagate, by natural convection, from the first portion of
the additional conduit structure to the second portion of the
additional conduit structure. The heated other gas is to propagate
through the second portion of the additional conduit structure and
to transfer heat to the other environment as the heated other gas
propagates through the second portion of the additional conduit
structure. The heated other gas is to cool during propagation
through the second portion of the additional conduit structure in
order to obtain cooled other gas. The additional conduit structure
defines a return portion for returning the cooled other gas to the
first portion of the additional conduit structure. The vault
cooling system is configured to remove heat from the one or more
than one vault during operation of the nuclear reactor and when the
nuclear reactor stops operating.
[0017] In some instances, the environment and the other environment
are the same.
[0018] In some embodiments, the environment is an outside
environment.
[0019] In another aspect, the present disclosure provides a cooling
system for a nuclear reactor. The system comprises: a conduit
structure defining a sealed closed circuit. The conduit structure
is formed outside the nuclear reactor. The conduit structure is to
hold a gas therein. The conduit structure has a first portion in
thermal contact with the nuclear reactor. The first portion is
configured to transfer heat from the nuclear reactor to the gas
present in the first portion. The heat transferred to the gas is to
heat the gas in order to obtain heated gas. The conduit structure
has a second portion located higher than the first portion. The
second portion is in thermal contact with an environment. The
conduit structure is configured for the heated gas to propagate, by
natural convection, from the first portion to the second portion.
The heated gas is to propagate through the second portion and to
transfer heat to the environment as the heated gas propagates
through the second portion. The heated gas is to cool during
propagation through the second portion in order to obtain cooled
gas. The conduit structure defines a return portion for returning
the cooled gas to the first portion. The cooling system is
configured to remove heat from the nuclear reactor when the nuclear
reactor stops operating and generates decay heat.
[0020] In some instances, the conduit structure comprises a closure
or more than one closure that prevents the gas from flowing through
the conduit structure when the nuclear reactor operates. In some
instances, the closure or more than one closure can be a louver or
more than one louver. In some instance, the cooling system can
comprise a controller configured to maintain the closure or more
than one closure closed when the nuclear reactor operates and to
open the closure or more than one closure when the reactor stops
operating.
[0021] In some instances, the first portion of the conduit
structure can be configured to receive heat from the nuclear
reactor through at least one of heat radiation, heat conduction,
and heat convection.
[0022] In some instances, the first portion can be cylindrically
shaped and surround the nuclear reactor.
[0023] In some instances, the second portion of the conduit
structure can define a wall.
[0024] In some instances, the second portion of the conduit
structure can further define a ceiling portion formed above the
wall portion.
[0025] In some instances, the second portion of the conduit
structure can further define a roof portion that extends over the
ceiling portion.
[0026] In some instances, the ceiling portion can extend from the
wall portion at an angle ranging between 2 and 10 degrees.
[0027] In some instances, the roof portion defines a dome.
[0028] In some instances, the second portion can comprise a cooling
tower.
[0029] In some instance, the conduit structure further comprises a
vault for storing spent nuclear fuel, a riser for fluidly
connecting the vault to the second portion, and an ancillary
conduit fluidly connecting the vault to the return portion.
[0030] In some instances, the gas can include at least one of air,
nitrogen and carbon dioxide.
[0031] In some instances, the system can further comprise one or
more than one vault for storing spent nuclear fuel; and a vault
cooling system for cooling the one or more than one vault. The
vault cooling system comprises: an additional conduit structure
defining an additional sealed closed circuit. The additional
conduits structure is to hold another gas therein. The additional
conduit structure has a first portion in thermal contact with the
one or more than vault. The first portion of the additional conduit
structure is configured to transfer heat from the one or more than
one vault to the other gas present in the first portion of the
additional conduit structure. The heat transferred to the other gas
to heat the other gas in order to obtain another heated gas. The
additional conduit structure has a second portion located higher
than the first portion and the second portion of the additional
conduit structure is in thermal contact with another environment.
The additional conduit structure is configured for the heated other
gas to propagate, by natural convection, from the first portion of
the additional conduit structure to the second portion of the
additional conduit structure. The heated other gas is to propagate
through the second portion of the additional conduit structure and
to transfer heat to the other environment as the heated other gas
propagates through the second portion of the additional conduit
structure. The heated other gas is to cool during propagation
through the second portion of the additional conduit structure in
order to obtain cooled other gas. The additional conduit structure
defines a return portion for returning the cooled other gas to the
first portion of the additional conduit structure. The vault
cooling system configured to remove heat from the one or more than
one vault during operation of the nuclear reactor and when the
nuclear reactor stops operating.
[0032] In some instances, the environment and the other environment
are the same.
[0033] In some embodiments, the environment is an outside
environment.
[0034] In another aspect, the present disclosure provides a cooling
system that comprises a nuclear reactor cooling system and a
distinct vault cooling system.
[0035] In same instances, the nuclear reactor cooling system
comprises: a conduit structure defining a sealed closed circuit.
The conduit structure is formed outside the nuclear reactor. The
conduit structure is to hold a gas therein. The conduit structure
has a first portion in thermal contact with the nuclear reactor.
The first portion is configured to transfer heat from the nuclear
reactor to the gas present in the first portion. The heat
transferred to the gas is to heat the gas in order to obtain heated
gas. The conduit structure has a second portion located higher than
the first portion. The second portion is in thermal contact with an
environment. The conduit structure is configured for the heated gas
to propagate, by natural convection, from the first portion to the
second portion. The heated gas is to propagate through the second
portion and to transfer heat to the environment as the heated gas
propagates through the second portion. The heated gas is to cool
during propagation through the second portion in order to obtain
cooled gas. The conduit structure defines a return portion for
returning the cooled gas to the first portion. The cooling system
is configured to continuously remove heat from the nuclear reactor
during operation of the nuclear reactor and when the nuclear
reactor stops operating and generates decay heat.
[0036] In some instances, the nuclear reactor cooling system
comprises a conduit structure defining a sealed closed circuit. The
conduit structure is formed outside the nuclear reactor. The
conduit structure is to hold a gas therein. The conduit structure
has a first portion in thermal contact with the nuclear reactor.
The first portion is configured to transfer heat from the nuclear
reactor to the gas present in the first portion. The heat
transferred to the gas is to heat the gas in order to obtain heated
gas. The conduit structure has a second portion located higher than
the first portion. The second portion is in thermal contact with an
environment. The conduit structure is configured for the heated gas
to propagate, by natural convection, from the first portion to the
second portion. The heated gas is to propagate through the second
portion and to transfer heat to the environment as the heated gas
propagates through the second portion. The heated gas is to cool
during propagation through the second portion in order to obtain
cooled gas. The conduit structure defines a return portion for
returning the cooled gas to the first portion. The cooling system
is configured to remove heat from the nuclear reactor when the
nuclear reactor stops operating and generates decay heat.
[0037] In some instances, the vault cooling system comprises an
additional conduit structure defining an additional sealed closed
circuit. The additional conduit structure is to hold another gas
therein. The additional conduit structure has a first portion in
thermal contact with the vault. The first portion of the additional
conduit structure is configured to transfer heat from the vault to
the other gas present in the first portion of the additional
conduit structure. The heat transferred to the other gas is to heat
the other gas in order to obtain heated other gas. The additional
conduit structure has a second portion located higher than the
first portion of the additional conduit structure. The second
portion of the additional conduit structure is in thermal contact
with another environment. The conduit structure is configured for
the heated other gas to propagate, by natural convection, from the
first portion of the additional conduit structure to the second
portion of the additional conduit structure. The heated other gas
is to propagate through the second portion of the additional
conduit structure and to transfer heat to the other environment as
the heated other gas propagates through the second portion of the
additional conduit structure. The heated other gas is to cool
during propagation through the second portion of the additional
conduit structure in order to obtain cooled other gas. The
additional conduit structure defines a return portion for returning
the cooled gas to the first portion. The vault cooling system is
configured to continuously remove heat from the vault.
[0038] In some instances, the vault cooling system comprises an
additional conduit structure defining an additional sealed closed
circuit. The additional conduit structure is to hold another gas
therein. The additional conduit structure has a first portion in
thermal contact with the vault. The first portion of the additional
conduit structure is configured to transfer heat from the vault to
the other gas present in the first portion of the additional
conduit structure. The heat transferred to the other gas is to heat
the other gas in order to obtain heated other gas. The additional
conduit structure has a second portion located higher than the
first portion of the additional conduit structure. The second
portion of the additional conduit structure is in thermal contact
with another environment. The conduit structure is configured for
the heated other gas to propagate, by natural convection, from the
first portion of the additional conduit structure to the second
portion of the additional conduit structure. The heated other gas
is to propagate through the second portion of the additional
conduit structure and to transfer heat to the other environment as
the heated other gas propagates through the second portion of the
additional conduit structure. The heated other gas is to cool
during propagation through the second portion of the additional
conduit structure in order to obtain cooled other gas. The
additional conduit structure defines a return portion for returning
the cooled gas to the first portion. The additional conduit
structure can comprises a closure or more than one closure that can
be actuated to prevent the other gas from flowing through the
additional conduit structure when the nuclear reactor operates. In
some instances, the closure or more than one closure can be a
louver or more than one louver.
[0039] In some instances and in all the aspects, instead of a gas
being used to cool the reactor and/or the vault, other suitable
fluids present in the conduit structure, partially in the liquid
phase and partially in the gaseous phase can be used. As an
example, water could be used.
BRIEF DESCRIPTION OF THE FIGURES
[0040] FIG. 1 shows a nuclear reactor system that includes an
embodiment of a cooling system in accordance with the present
disclosure.
[0041] FIG. 2 shows a nuclear reactor system that includes another
embodiment of a cooling system in accordance with the present
disclosure.
[0042] FIG. 3 shows a nuclear reactor system that includes yet
another embodiment of a cooling system in accordance with the
present disclosure.
[0043] FIG. 4 shows a nuclear reactor system that includes an
additional embodiment of a cooling system in accordance with the
present disclosure.
[0044] FIG. 5 shows an embodiment of a conduit with a closure that
can be used to stop a gas from flowing in some embodiments of the
cooling system in accordance with the present disclosure.
DETAILED DESCRIPTION
[0045] The cooling system of the present disclosure allows for
decay heat removal from a nuclear core of a nuclear reactor when
the nuclear reactor cesses to operate due to unforeseen conditions
such as, for example, loss of electrical power to pumps circulating
the primary coolant in the nuclear reactor. The cooling system of
the present disclosure has a conduit structure that defines a
sealed closed circuit through which a cooling fluid (a gas or a two
phase gas/liquid) circulates through natural convection. In some
embodiments, the cooling system of the present disclosure is always
functioning, that is, the cooling system continuously extracts heat
from the nuclear core. In these embodiments, the cooling system
does not need to be actuated in any way when the nuclear reactor
shuts down unexpectedly. The heat extracted by the cooling system
during operation of the nuclear reactor is wasted instead of being
used externally to perform work (e.g. to power an electrical
generator). However, the fraction of the heat wasted can be of the
order of 1% or less, which can be seen as being a small cost to pay
for the benefit of having increased control over decay heat
management. As an additional benefit, always having the cooling
system running helps cool the silo environment in which the nuclear
reactor is disposed, which keeps the reactor vessel (the vessel
that contains the nuclear core) at a lower operating
temperature.
[0046] Alternatively, in other embodiments, the cooling system of
the present disclosure can be actively or passively activated. For
example, in such embodiments, louvers (or any other suitable type
of closures) can be installed in the cooling system and configured
to open upon loss of electrical power. Opening of the louvers
allows the cooling system to effectively remove decay heat when
needed. In other embodiments, the louvers can be controlled by an
operator and actuated at any time.
[0047] FIG. 1 shows an embodiment of a nuclear reactor system 10
that comprises a cooling system in accordance with the present
disclosure. The nuclear reactor system 10 has a reactor 12 (reactor
vessel that contains the reactor core) contained in a guard vessel
14. The reactor 12 can be any suitable type of nuclear reactor such
as, for example, a molten salt nuclear reactor. The guard vessel 14
is in thermal contact with the reactor 12. That is, some heat
generated by the reactor 12 is transferred to the guard vessel 14,
by heat radiation, conduction, and/or convection. In other
embodiments that are within the scope of the present disclosure,
there may not be a guard vessel.
[0048] The nuclear reactor system 10 comprises a cooling system 16,
which can include any suitable type of conduit structure that
defines a sealed closed circuit in which a fluid (a coolant fluid)
can circulate. In the context of the present disclosure, a sealed
closed circuit is a circuit that retains the fluid circulating
therein without releasing the fluid to the atmosphere. The sealed
closed circuit is not in fluid communication with the atmosphere
during operation of the cooling system. However, the sealed closed
circuit may have access ports to insert and/or remove fluid in/from
the sealed closed circuit when the cooling system is not in
operation. In the context of the present disclosure, having a fluid
communication between objects or spaces means that there is path
for fluid to flow between the objects or spaces.
[0049] Further, the conduit structure is not in the reactor itself
and the heat removed by the conduit structure is not used to
perform work. That is, the conduit structure is formed outside the
nuclear reactor. As such, the fluid circulating in the conduit
structure is not a coolant used to remove heat from the nuclear
reactor core and to transfer that heat to electrical generators or
any device that can perform work.
[0050] The cooling system 16 has a portion 18 (bottom portion or
first portion or heat source portion) that is in thermal contact
with the reactor 12 and/or the guard vessel 14. That is, the bottom
portion 18 is positioned to receive heat generated by the reactor
12 and/or the guard vessel 14, through heat radiation, conduction,
and/or convection. The heat generated by the nuclear core is
transmitted out of the nuclear reactor core through the vessel wall
of the nuclear reactor. The gas present and/or circulating in the
cooling system 16, at the portion 18, is heated by the heat
received from the reactor 12 and/or the guard vessel 14. The heated
gas at the bottom portion 18 will naturally tend to rise in the
cooling system 16.
[0051] The bottom portion 18 can have any suitable form. For
example, the bottom portion 18 can be cylinder-shaped with a
diameter selected to surround the reactor 12 and or the guard
vessel 14. A cylinder-shaped bottom portion can have, in some
embodiments a flooring portion disposed beneath the reactor 12
and/or the guard vessel 14. The bottom portion 18 does not need to
be cylinder-shaped.
[0052] The cooling system 16 comprises a floor portion 19 and a
wall portion 20 that extends vertically to allow the heated gas to
rise. The floor portion 19 can be at any suitable angle what will
allow heated gas to move from the bottom portion to the wall
portion 20. The wall portion 20 can extend vertically at any
suitable angle that allows heated gas to rise. The cooling system
16 further comprises a ceiling portion 22 and a roof portion 24. As
such, the gas heated at the bottom portion 18 moves (rises),
through convection, towards the floor portion 19, moves laterally
outwards in the floor portion 19, reaches the wall portion 20,
rises in the wall portion 20, reaches the ceiling portion 22, and
then the roof portion 24. The ceiling portion 22 can extend from
the wall portion at any suitable angle. For example, in some
embodiment, the angle can range from 2 to 10 degrees.
[0053] The floor portion 19, the wall portion 20, the ceiling
portion 22 and the roof portion 24 can be considered as being part
of a second portion of the conduit structure.
[0054] As the heated gas moves from the bottom portion 18 toward
the roof portion 24, it dissipates heat to the environment
surrounding the cooling system and cools. The roof portion 24 can
be in contact with the outside atmosphere to allow efficient heat
transfer from the roof portion 24 to the outside atmosphere. The
materials used for the various portions of the cooling system 16
can be selected to allow optimal heat transfer from the cooling
system to the environment that is in contact with the various
portions of the cooling system. For example, the material can be,
in some embodiments, stainless steel or mild steel.
[0055] The hot gas that has cooled while circulating toward the
roof portion 24 is then directed towards where it started its
ascent. That is, the cooled gas at the roof portion 24 is directed
to the bottom portion 18 of the cooling system 16. As shown at FIG.
1, the roof portion 24 is slanted towards the outer periphery of
the nuclear reactor system 10. The roof portion 24 in FIG. 1
defines a dome; however, this need not be the case. The roof
portion can have any suitable shape (e.g., it can define a slanted
plane). There, a return portion 26 connects the roof portion 24 to
the bottom portion 18, where the cycle is repeated. In the present
embodiment, the return portion 26 can be considered as being part
of the wall portion. In this case, the wall portion has a section
in which the fluid rises toward the ceiling and roof, and an
adjoining section where the fluid descends toward the bottom
portion 18. In other embodiments, the return portion can be
distinct from the wall portion and have any suitable shape (e.g.,
cylindrical shape, pillar shape, etc.)
[0056] The ceiling portion and the roof portion do not need to
strictly be a ceiling or a roof, respectively. That is, the ceiling
portion 22 can have another structure, not necessarily part of the
cooling system, formed beneath that would block the ceiling portion
22 from view. With respect to the roof portion 24, it can have a
further structure, not necessarily part of the cooling system,
formed above it, which would block the roof portion 26 from view.
As such, the ceiling portion can be referred to as a first upper
portion and the roof portion can be referred to as a second upper
portion. The first upper portion and/or the second upper portion
can be covered from view.
[0057] In FIG. 1, the arrows 28 and 30 indicate the direction of
flow of the gas in the cooling system 16. Arrows 28 indicate gas
that is rising while arrows 30 indicate gas that is descending.
[0058] As will be understood by the skilled worker, the
cross-section area of the aforementioned portions of the cooling
system 16 can be dimensioned to have the gas circulate, through the
cooling system, at a constant speed. That is, as will be understood
by the worker skilled in the art, cross-section areas of portions
of the cooling system where the gas is cooler can be smaller than
portions where the gas is hotter.
[0059] In other embodiments, instead of having a single phase
coolant, such as a gas, it is possible to have a two phase coolant
such as, for example, water. When such a two phase coolant is used,
coolant in the liquid phase, present at the portion 18, extracts
heat from the reactor 12 and/or guard vessel 14. Eventually, when
the coolant has extracted a sufficient quantity of heat, it changes
into the gas phase and begins moving towards the roof portion 24.
At the roof portion 24, the coolant, having sufficiently cooled,
returns to the liquid phase and drips down toward the portion 18,
where the cycle is repeated. In some embodiments, it is possible
for the coolant to change from the gas phase to the liquid phase
prior to reaching the roof portion 24, and to drip back toward the
portion 18, in the same portion of the cooling system 18 through
which the coolant--in the gas phase--rose.
[0060] As the cooling system 16 circulates a gas or liquid in close
proximity to the nuclear reactor 12, the possibility of radioactive
activation of the gas or liquid by neutrons escaping the reactor
vessel exists. However as the cooling system 16 is a closed loop
(closed circuit), it prevents any emission of activated products to
the atmosphere. If and when there is a leak of any radioactive
material from the reactor 12 into the cooling system 16, again, as
the cooling system is designed as a closed loop, any release of
radioactive material to the atmosphere can be avoided.
[0061] Further, in the event where the cooling system 16 should
become open (e.g., breakage of the roof) and air enter the cooling
system, the cooling of the reactor 12 and/or guard vessel 14 would
become more efficient and not lead to overheating of the reactor
12. That is, the removal of decay heat would not be adversely
affected. In any such situation, the nuclear reactor can be
shutdown to reduce to a negligible amount any neutron fluence
reaching the cooling system 16. As such, if the now open cycle
cooling system 16 is circulating air in the vicinity of the reactor
(e.g., portion 18), very little radioactive activation products
such as Argon 41 (.sup.41Ar) would be produced and/or released to
the atmosphere.
[0062] In other embodiments, the cooling system, instead of having
a roof as shown in FIG. 1, could instead have a conduit structure
that circulates the coolant outside of the building where the
reactor is housed. For example, the conduit structure in question
could be located outside, at the side of building in question. Such
a conduit structure transferring heat to the atmosphere would be at
a higher elevation than the reactor and/or guard vessel to ensure
natural circulation of the fluid in the conduit structure of the
cooling system.
[0063] FIG. 2 shows a cut-away view of such an embodiment of the
cooling system of the present disclosure connected to a nuclear
reactor. In this embodiment, the cooling system 32 has a conduit
structure with a heat source portion 34 (first portion) that
surrounds the nuclear reactor and/or its guard vessel (not shown).
The heat source portion 34 is in thermal contact with the nuclear
reactor and/or the guard vessel. The cooling system 32 defines a
closed circuit 36 through which a gas 38 circulates through
convection. The arrows 40 indicate the direction taken by the gas
38 as it flows through the cooling system 32. The cooling system 32
has a cooling tower 42 located outside the building 44 in which the
nuclear reactor and its guard vessel are housed. The cooling tower
42 can be designed with openings such as opening 46 al its bottom
section, in order to allow for air to circulate, as indicated by
arrow 48, from the outside of the cooling tower through the cooling
tower 42 (which can be considered a second portion of the conduit
structure). The cooling tower can define a hyperbolic shape. The
heat source portion 34 is connected to cooling tower 42 through
conduits 53. Although not apparent from FIG. 2, the outside
portions 55 of the cooling tower 42 are in fluid communication with
each other and, the inside portions 57 of the cooling tower 42 are
in fluid communication with each other. And, clearly, the inside
portions are in fluid communication with the outside portions. As
would be understood by one skilled in the art, such a cooling tower
arrangement allows for a strong updraft of the outside air up
through the tower which aids in heat removal from the cooling
system 32 and increases the heat transfer coefficient, which
results in a lowering of needed surface area of the cooling
tower.
[0064] The heat source portion 34 is configured to have the gas 38
circulate therein. Gas that has received heat from the nuclear
reactor and the guard vessel while propagating in the heat source
portion 34 rises and exits the first portion 34 at the first
connection 50. This hot gas dissipates its heat as it circulates
though the cooling tower 42 and re-enters the heat source portion
34 at connection 52.
[0065] In addition to cooling the guard vessel and/or the reactor
itself, the cooling system of the present disclosure can be used to
cool any other part of the facility in which the reactor is
installed. For example, in some instances, the facility in question
may have a section for storing spent nuclear fuel such as, for
example, spent molten fuel salt. In such facilities, the cooling
system used for cooling the reactor and/or guard vessel can be
configured to also cool the area of the facility where the spent
nuclear fuel is stored. In other embodiments, a separate cooling
system can be used and the separate cooling system can be a
duplicate or a scaled duplicate of the cooling used by the reactor
and/or guard vessel.
[0066] FIG. 3 shows a cross-sectional view of yet another
embodiment of the cooling system 33 of the present disclosure,
connected to a nuclear reactor. In this embodiment, the cooling
system 33 is connected to (i.e., is in thermal contact with) a heat
source portion 34 (first portion) surrounding the nuclear reactor
and its guard vessel (not shown). The cooling system 33 defines a
closed circuit 36 through which a gas 38 circulates through
convection. The arrows 40 indicate the direction taken by the gas
38 as it flows through the cooling system 33. The cooling system 33
has a wall portion 20, a ceiling portion 22, a roof portion 24, a
vault portion 54 and a riser portion 56.
[0067] The vault portion 54 contains or is designed to contain
spent nuclear fuel such as, for example, spent molten fuel salt, in
a container 60. The gas in the vault 54 is in thermal contact with
the container 60 and is heated by the spent nuclear fuel through
the container 60. The heated gas rises from the vault 54 to the
ceiling portion 22, through a riser 56. That is, the riser 56 is
part of the cooling system 33 and interconnects the vault 54 to the
ceiling portion 22. Upon reaching the ceiling portion 22, the gas
received from the riser 56 continues to rise and propagate in the
ceiling portion 22 up to the opening 62, which connects (fluidly
connects) the ceiling portion 22 to the roof portion 24. As the gas
cools, it propagates downward in the roof portion 24 and the wall
portion 20. The cooled gas continues to propagate in the conduit
section 66 towards the guard vessel 34. Part of the cooled gas is
branched out of the conduit section 66 into an ancillary conduit 68
that connects the conduit section 66 to the vault 54. When the
cooled gas arrives at the vault 54, the cycle where the gas
extracts heat from the spent nuclear fuel, propagates up through
the riser 56 and subsequently returns to the vault, is repeated.
Even though only one vault 54 is shown in FIG. 3, any number of
vaults can be connected to and be part of the cooling system
33.
[0068] The gas in the conduit section 66 that returns to the heat
source portion 34 is heated by the guard vessel and/or reactor. The
heated gas rises in the heat source portion 34 and exits the heat
source portion 34 into the conduit section 70. The gas then
propagates upwardly in the wall portion 20, reaches the ceiling
portion 22, and then the roof portion 24, and then back down toward
the heat source portion 34.
[0069] As the heated gas moves from the conduit portion 70 toward
the roof portion 24, it dissipates heat to the environment
surrounding the cooling system and cools. The roof portion 24 can
be in contact with the outside atmosphere to allow efficient heat
transfer from the roof portion 24 to the outside atmosphere. The
materials used for the various portions of the cooling system 16
can be selected to allow optimal heat transfer from the cooling
system to the environment that is in contact with the various
portions of the cooling system.
[0070] FIG. 4 shows an additional cooling system 100 In accordance
with the present disclosure. The cooling system 100 comprises the
cooling system 90, which is configures to cool the nuclear reactor
only. The cooling system 90 is essentially the same as the cooling
system 33 of FIG. 3 but is not configured to cool any type of
vault. Returning to FIG. 4, the vault 54, which represents one or
more than one vault, has a dedicated cooling system 92 that works
similarly to the cooling system 90. The vault 54 has a first
portion 102 connected thereto and in thermal contact therewith. The
first portion connects, through a riser 56, to a ceiling portion
104 and a roof portion 106. A return portion (another conduit) 108
returns the cooled gas to the vault 54. The vault 54, riser 56,
celling 104, roof 106 and return portion 108 define a sealed
conduit structure that is configured to contain a fluid used for
cooling the vault 54.
[0071] FIG. 5 shows a cutaway view of a conduit 200 that can be
part of the above described embodiments. The conduit 200 has a
louver 202 installed therein in accordance. The louver is in the
open position and allows gas to flow in the conduit structure. The
closed position is defined, in this embodiment, by the louver being
horizontally disposed (not shown), rather than obliquely as in this
figure. The louver 202 is connected to a louver actuator 204 that
allows the louver 202 to open when power to the louver controller
204 is lost. Closures other than louvers can be used without
departing from the scope of the present disclosure. Such closures
can be installed anywhere in the conduit structures that define a
sealed closed loop through which a cooling fluid circulates to cool
either a nuclear reactor, a spent fuel vault, or both.
[0072] The cooling system of the present disclosure allows for
decay heat removal from a nuclear core of a nuclear reactor when
the nuclear reactor cesses to operate due to unforeseen conditions
such as, for example, loss of electrical power to pumps circulating
the primary coolant in the nuclear reactor. In some embodiments,
the cooling system of the present disclosure is always functioning,
that is, is always extracting heat from the nuclear core, the
cooling system does not need to be actuated in any way when the
nuclear reactor shuts down unexpectedly. In these embodiments, the
heat extracted by the cooling system during operation of the
nuclear reactor is wasted instead of being used externally to
perform work (e.g., to power an electrical generator). However, the
fraction of the heat wasted can be of the order of 1% or less,
which can be seen as being a small cost pay for the benefit of
having increased control over decay heat management. In other
embodiments, closures disposed in the cooling system allow the
cooling system to be turned on and off, either automatically upon
loss of electrical power or deliberately by an operator.
[0073] In the preceding description, for purposes of explanation,
numerous details are set forth in order to provide a thorough
understanding of the embodiments. However, it will be apparent to
one skilled in the art that these specific details are not
required.
[0074] The above-described embodiments are intended to be examples
only. Alterations, modifications and variations can be effected to
the particular embodiments by those of skill in the art without
departing from the scope, which is defined solely by the claims
appended hereto.
* * * * *